I believe most domestic made exhausts for the NSX like comptech are CARB exempt and will pass smog no problem. However, from my experience, they can never tell its aftermarket anyways, especially from an NSX. But if you are paranoid, then look for headers and exhausts that are CARB exempt. I think comptech & DC are, not sure about RM.
I have an RM DTM exhaust. Didn't have a problem when I got my last check. On my other cars, never had a problem either even with different brands of catback or axel back exhausts. The guys doing the checks always seemed more concerned with mods in the engine bay, things like headers, intakes, etc. Just make sure you get stuff that's CARB certified. They should have a list of aftermarket items that have passed certification. (Assuming they update the list. I went to one place that had a list from 1995 and wouldn't pass my 97 Integra with an AEM CAI.) Some experienced smog techs will even know what manufacturers and parts have certification and don't even bother checking the list and just pass you visually anyways. (The second tech I took my Integra knew all about AEM CAIs and just said "Bah, I know those are certified already. I don't need to check my list," and proceeded on with the emission testing.
AFAIK, the Comptech Header, DC Sports Header, Comptech Exhaust, and DC Sports Exhaust are the only CARB certified exhaust products currently available for the NSX. CARB certified will allow the product to clear the visual. If anything was to create an emissions problem, it would still be liable to require a failure.
On an emissions standpoint, any cat-back exhaust should not affect the emissions readings.